Electrical and electronic utility devices, including but not limited to portable communication devices, such as telephone craftsperson's test sets, radios, cassette and CD players, and the like, are typically configured to be powered from alternative DC power sources--in particular, batteries installed in an internal battery compartment, or by means of an internal AC-DC converter (rectifier and voltage scaling circuit) that is plugged into a local (110 VAC) outlet. If the device is equipped to use rechargeable batteries (as is customarily the case), such batteries may be charged by connecting a DC charging port of the device to a battery charging unit plugged into a (110 VAC) power outlet.
Typically, a device's battery compartment is configured to accept batteries of only a particular size, such as D, C, A, AA, or AAA type batteries, dictated by the power requirements of the device. Where the device is designed for use with increased storage capacity rechargeable batteries (e.g., 11/2 AA NiCad batteries), that are sized differently from (longer than) conventional non-rechargeable (e.g., AA alkaline) batteries, the battery compartment of the device will be sized correspondingly to accept only such longer rechargeable batteries. As a consequence, as such rechargeable batteries become depleted, they must be replaced by like sized rechargeable batteries, since conventional non-rechargeable batteries of the same voltage, but lesser capacity, won't fit.
This creates a frustrating situation to the user, particularly where utilization of the device may be relatively short term, and readily available non-rechargeable batteries would do the trick--if only they would fit in the battery compartment. An example of this problem is the need for an abbreviated use of a telephone test set in the course of a craftsperson servicing a subscriber line circuit. If the rechargeable batteries go dead in the field, the test set cannot be used until the batteries are recharged.